Obtaining images via cameras or cameras integrated within devices such as mobile phones or tablets or the like is very common. In some conditions such as low light exposure conditions, the imaging device (e.g., a camera or a device having an integrated camera) may implement a flash in an attempt to properly expose the scene. For example, the imaging device may implement a global flash (e.g., a flash light) during exposure. However, when subjects of the scene are at different distances from the flash, some subjects may be overexposed or underexposed. For example, if a first subject is close to the flash and a second subject is farther from the flash, properly exposing the second subject may cause overexposure of the first subject (e.g., the first subject being too bright) and properly exposing the first subject may cause underexposure of the second subject (e.g., the second subject being too dark). For example, a global flash may illuminate subjects according to the inverse-square law such that flash intensity at a distance from the flash is proportional to the inverse square of the distance (e.g., flash intensity=1/distance2). In such situations, a single exposure using a global flash may provide low quality images.
Current techniques may attempt to overcome such difficulties using high-dynamic-range imaging (HDR) and underexposure and local contrast enhancement. For example, HDR imaging may include taking multiple images of the scene with different exposure settings and combining the resultant images. However, the use of such multiple images may introduce problems such as blurring, ghosting effects, and the requirement that the scene remain unchanged while the multiple images are obtained. Furthermore, HDR imaging may not work in video capture mode at high frame rates (e.g., if the time between video frames is less than the time needed to obtain the multiple images) and HDR imaging may be computationally intensive and therefore not suitable for low-power devices.
In underexposure and local contrast enhancement techniques, the scene may be underexposed such that none of the subjects are overexposed (e.g., overexposed to saturation) and local contrast enhancement techniques may be used to brighten any underexposed subjects. However, such techniques may increase image noise in the enhanced image areas and/or create unsatisfactory image results due to very low signal levels representing the underexposed (e.g., dark) subjects in the original (e.g., captured) image data. For example, the underexposed subjects may not be able to be suitably represented based on local contrast enhancement techniques.
As such, existing techniques do not provide suitable exposure for subjects in a scene that are at different distances from the global flash. Furthermore, techniques for overcoming such difficulties may be impracticable and/or may provide low quality and unnatural looking images. It is with respect to these and other considerations that the present improvements have been needed. Such improvements may become critical as the desire to obtain aesthetically pleasing images in a variety of contexts becomes more widespread.